Internet Engineering Task Force (IETF) A. Malis, Ed.
Request for Comments: 6827 Verizon Communications
Obsoletes: 5787 A. Lindem, Ed.
Updates: 5786 Ericsson
Category: Standards Track D. Papadimitriou, Ed.
ISSN: 2070-1721 Alcatel-Lucent
January 2013
Automatically Switched Optical Network (ASON)Routing for OSPFv2 Protocols
Abstract
The ITU-T has defined an architecture and requirements for operating
an Automatically Switched Optical Network (ASON).
The Generalized Multiprotocol Label Switching (GMPLS) protocol suite
is designed to provide a control plane for a range of network
technologies. These include optical networks such as time division
multiplexing (TDM) networks including the Synchronous Optical
Network/Synchronous Digital Hierarchy (SONET/SDH), Optical Transport
Networks (OTNs), and lambda switching optical networks.
The requirements for GMPLS routing to satisfy the requirements of
ASON routing and an evaluation of existing GMPLS routing protocols
are provided in other documents. This document defines extensions to
the OSPFv2 Link State Routing Protocol to meet the requirements for
routing in an ASON.
Note that this work is scoped to the requirements and evaluation
expressed in RFC 4258 and RFC 4652 and the ITU-T Recommendations that
were current when those documents were written. Future extensions or
revisions of this work may be necessary if the ITU-T Recommendations
are revised or if new requirements are introduced into a revision of
RFC 4258. This document obsoletes RFC 5787 and updates RFC 5786.
Malis, et al. Standards Track [Page 1]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6827.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Malis, et al. Standards Track [Page 2]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20131. Introduction
The Generalized Multiprotocol Label Switching (GMPLS) [RFC3945]
protocol suite is designed to provide a control plane for a range of
network technologies. These include optical networks such as time
division multiplexing (TDM) networks including SONET/SDH, Optical
Transport Networks (OTNs), and lambda switching optical networks.
The ITU-T defines the architecture of the Automatically Switched
Optical Network (ASON) in [G.8080].
[RFC4258] describes the routing requirements for the GMPLS suite of
routing protocols to support the capabilities and functionality of
ASON control planes identified in [G.7715] and in [G.7715.1].
[RFC4652] evaluates the IETF Link State routing protocols against the
requirements identified in [RFC4258]. Section 7.1 of [RFC4652]
summarizes the capabilities to be provided by OSPFv2 [RFC2328] in
support of ASON routing. This document describes the OSPFv2
specifics for ASON routing.
Multi-layer transport networks are constructed from multiple networks
of different technologies operating in a client-server relationship.
The ASON routing model includes the definition of routing levels that
provide scaling and confidentiality benefits. In multi-level
routing, domains called routing areas (RAs) are arranged in a
hierarchical relationship. Note that as described in [RFC4652],
there is no implied relationship between multi-layer transport
networks and multi-level routing. The multi-level routing mechanisms
described in this document work for both single-layer and multi-layer
networks.
Implementations may support a hierarchical routing topology (multi-
level) for multiple transport network layers and/or a hierarchical
routing topology for a single transport network layer.
This document describes the processing of the generic (technology-
independent) link attributes that are defined in [RFC3630],
[RFC4202], and [RFC4203] and that are extended in this document. As
described in Section 5.2, technology-specific traffic engineering
attributes and their processing may be defined in other documents
that complement this document.
Malis, et al. Standards Track [Page 4]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
Note that this work is scoped to the requirements and evaluation
expressed in [RFC4258] and [RFC4652] and the ITU-T Recommendations
that were current when those documents were written. Future
extensions or revisions of this work may be necessary if the ITU-T
Recommendations are revised or if new requirements are introduced
into a revision of [RFC4258].
1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The reader is assumed to be familiar with the terminology and
requirements developed in [RFC4258] and the evaluation outcomes
described in [RFC4652].
General ASON terminology is provided in Appendix A. ASON routing
terminology is described in Appendix B.
2. Routing Areas, OSPF Areas, and Protocol Instances
An ASON routing area (RA) represents a partition of the transport
plane, and its identifier is used within the control plane as the
representation of this partition.
RAs are hierarchically contained: a higher-level (parent) RA contains
lower-level (child) RAs that in turn MAY also contain RAs. Thus, RAs
contain RAs that recursively define successive hierarchical RA
levels. Routing information may be exchanged between levels of the
RA hierarchy, i.e., Level N+1 and N, where Level N represents the RAs
contained by Level N+1. The links connecting RAs may be viewed as
external links (inter-RA links), and the links representing
connectivity within an RA may be viewed as internal links (intra-RA
links). The external links to an RA at one level of the hierarchy
may be internal links in the parent RA. Intra-RA links of a child RA
MAY be hidden from the parent RA's view [RFC4258].
An ASON RA can be mapped to an OSPF area, but the hierarchy of ASON
RA levels does not map to the hierarchy of OSPF areas. Instead,
successive hierarchical levels of RAs MUST be represented by separate
instances of the protocol. Thus, inter-level routing information
exchange (as described in Section 7) involves the export and import
of routing information between protocol instances.
Malis, et al. Standards Track [Page 5]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
An ASON RA may therefore be identified by the combination of its OSPF
Instance ID and its OSPF Area ID. With proper and careful network-
wide configuration, this can be achieved using just the OSPF Area ID,
and this process is RECOMMENDED in this document. These concepts are
discussed in Section 7.
A key ASON requirement is the support of multiple transport planes or
layers. Each transport node has associated topology (links and
reachability), which is used for ASON routing.
3. Terminology and Identification
This section describes the mapping of key ASON entities to OSPF
entities. Appendix A contains a complete glossary of ASON routing
terminology.
There are three categories of identifiers used for ASON routing
(G.7715.1): transport-plane names, control-plane identifiers for
components, and Signaling Communications Network (SCN) addresses.
This section discusses the mapping between ASON routing identifiers
and corresponding identifiers defined for GMPLS routing and how these
support the physical (or logical) separation of transport-plane
entities and control-plane components. GMPLS supports this
separation of identifiers and planes.
In the context of OSPF Traffic Engineering (TE), an ASON transport
node corresponds to a unique OSPF TE node. An OSPF TE node is
uniquely identified by the TE Router Address TLV [RFC3630]. In this
document, the TE Router Address is referred to as the TE Router ID.
In GMPLS, TE router addresses are advertised as reachable in both the
control and transport planes, see Section 4 below. Furthermore, the
TE Router ID should not be confused with the OSPF Router ID that
uniquely identifies an OSPF router within an OSPF routing domain
[RFC2328] and is in a name space for control-plane components.
The Router Address top-level TLV definition, processing, and usage
are largely unchanged from [RFC3630]. This TLV specifies a stable
OSPF TE node IP address, i.e., the IP address is always reachable
when there is IP connectivity to the associated OSPF TE node.
ASON defines a Routing Controller (RC) as an entity that handles
(abstract) information needed for routing and the routing information
exchange with peering RCs by operating on the Routing Database (RDB).
ASON defines a Protocol Controller (PC) as an entity that handles
protocol-specific message exchanges according to the reference point
over which the information is exchanged (e.g., E-NNI, I-NNI) and
internal exchanges with the RC [RFC4258]. In this document, an OSPF
router advertising ASON TE topology information will perform both the
Malis, et al. Standards Track [Page 6]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
functions of the RC and PC. The OSPF routing domain comprises the
control plane, and each OSPF router is uniquely identified by its
OSPF Router ID [RFC2328].
4. Reachability
In ASON, reachability information describes the set of endpoints that
are reachable by the associated node in the transport plane.
Reachability information represents transport-plane resources, e.g.,
an optical cross-connect interface, and uses transport-plane
identifiers.
In order to advertise blocks of reachable address prefixes, a
summarization mechanism is introduced that is based on the techniques
described in [RFC5786]. For ASON reachability advertisement, blocks
of reachable address prefixes are advertised together with the
associated transport-plane node. The transport-plane node is
identified in OSPF TE Link State Advertisements (LSAs) by its TE
Router ID, as discussed in Section 6.
In order to support ASON reachability advertisement, the Node
Attribute TLV defined in [RFC5786] is used to advertise the
combination of a TE Router ID and its set of associated reachable
address prefixes. The Node Attribute TLV can contain the following
sub-TLVs:
- Local TE Router ID sub-TLV: Length: 4; Defined in Section 6.2
- Node IPv4 Local Address sub-TLV: Length: variable; [RFC5786]
- Node IPv6 Local Address sub-TLV: Length: variable; [RFC5786]
A router may support multiple transport nodes as discussed in
Section 6 and, as a result, may be required to advertise reachability
separately for each transport node. As a consequence, it MUST be
possible for the router to originate more than one TE LSA containing
the Node Attribute TLV when used for ASON reachability advertisement.
Hence, the Node Attribute TLV [RFC5786] advertisement rules are
relaxed. A Node Attribute TLV MAY appear in more than one TE LSA
originated by the RC when the RC is advertising reachability
information for a different transport node identified by the Local TE
Router sub-TLV (refer to Section 6.2).
As specified in [RFC3630], TE-advertised router addresses are also
advertised as reachable in the control plane and are therefore also
valid identifiers in the ASON SCN name space.
Malis, et al. Standards Track [Page 7]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20135. Link Attribute
With the exception of local adaptation (described below), the mapping
of link attributes and characteristics to OSPF TE Link TLV sub-TLVs
is unchanged [RFC4652]. OSPF TE Link TLV sub-TLVs are described in
[RFC3630] and [RFC4203]. Advertisement of this information SHOULD be
supported on a per-layer basis, i.e., one TE LSA per unique switching
capability and bandwidth granularity combination.
5.1. Local Adaptation
Local adaptation is defined as a TE link attribute (i.e., sub-TLV)
that describes the cross/inter-layer relationships.
The Interface Switching Capability Descriptor (ISCD) TE Attribute
[RFC4202] identifies the ability of the TE link to support cross-
connection to another link within the same layer. When advertising
link adaptation, it also identifies the ability to use a locally
terminated connection that belongs to one layer as a data link for
another layer (adaptation capability). However, the information
associated with the ability to terminate connections within that
layer (referred to as the termination capability) is advertised with
the adaptation capability.
For instance, a link between two optical cross-connects will contain
at least one ISCD attribute describing the Lambda Switching Capable
(LSC) switching capability. Conversely, a link between an optical
cross-connect and an IP/MPLS Label Switching Router (LSR) will
contain at least two ISCD attributes, one for the description of the
LSC termination capability and one for the Packet Switching Capable
(PSC) adaptation capability.
In OSPFv2, the Interface Switching Capability Descriptor (ISCD) is a
sub-TLV (type 15) of the top-level Link TLV (type 2) [RFC4203]. The
adaptation and termination capabilities are advertised using two
separate ISCD sub-TLVs within the same top-level Link TLV.
An interface MAY have more than one ISCD sub-TLV, per [RFC4202] and
[RFC4203]. Hence, the corresponding advertisements should not result
in any compatibility issues.
Malis, et al. Standards Track [Page 8]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20135.2. Bandwidth Accounting
GMPLS routing defines an ISCD that provides, among other things, the
quantities of the maximum/minimum available bandwidth per priority
for Label Switched Paths (LSPs). One or more ISCD sub-TLVs can be
associated with an interface, per [RFC4202] and [RFC4203]. This
information, combined with the Unreserved Bandwidth Link TLV sub-TLV
[RFC3630], provides the basis for bandwidth accounting.
In the ASON context, additional information may be included when the
representation and information in the other advertised fields are not
sufficient for a specific technology, e.g., SDH. The definition of
technology-specific information elements is beyond the scope of this
document. Some technologies will not require additional information
beyond what is already defined in [RFC3630], [RFC4202], and
[RFC4203].
6. Routing Information Scope
For ASON routing, the control-plane component routing adjacency
topology (i.e., the associated Protocol Controller (PC) connectivity)
and the transport topology are not assumed to be congruent [RFC4258].
Hence, a single OSPF router (i.e., the PC) MUST be able to advertise
on behalf of multiple transport-layer nodes. The OSPF routers are
identified by OSPF Router ID, and the transport nodes are identified
by TE Router ID.
The Router Address TLV [RFC3630] is used to advertise the TE Router
ID associated with the advertising Routing Controller (RC). TE
Router IDs for additional transport nodes are advertised through
specification of the Local TE Router Identifier in the Local and
Remote TE Router TE sub-TLV and the Local TE Router Identifier
sub-TLV described in the sections below. These Local TE Router
Identifiers are typically used as the local endpoints for TE LSPs
terminating on the associated transport node.
The use of multiple OSPF Routers to advertise TE information for the
same transport node is not considered a required use case and is not
discussed further in this document.
6.1. Link Advertisement (Local and Remote TE Router ID Sub-TLV)
When an OSPF Router advertises on behalf of multiple transport nodes,
the link endpoints cannot be automatically assigned to a single
transport node associated with the advertising router. In this case,
the local and remote transport nodes MUST be identified by TE Router
ID to unambiguously specify the transport topology.
Malis, et al. Standards Track [Page 9]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
For this purpose, a new sub-TLV of the OSPFv2 TE LSA top-level Link
TLV is introduced that defines the Local and Remote TE Router ID.
The Type field of the Local and Remote TE Router ID sub-TLV is
assigned the value 10 (see Section 10). The Length field takes the
value 8. The Value field of this sub-TLV contains 4 octets of the
Local TE Router Identifier followed by 4 octets of the Remote TE
Router Identifier. The value of the Local and Remote TE Router
Identifier MUST NOT be set to 0.
The format of the Local and Remote TE Router ID sub-TLV is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (10) | Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV MUST be included as a sub-TLV of the top-level Link TLV
if the OSPF router is advertising on behalf of one or more transport
nodes having TE Router IDs different from the TE Router ID advertised
in the Router Address TLV. For consistency, this sub-TLV MUST be
included when OSPF is used for the advertisement of ASON information
as described herein. If it is not included in a Link TLV, or if a
value of 0 is specified for the Local or Remote TE Router Identifier,
the Link TLV will not be used for transport-plane path computation.
Additionally, the condition SHOULD be logged for possible action by
the network operator.
Note: The Link ID sub-TLV identifies the other end of the link (i.e.,
Router ID of the neighbor for point-to-point links) [RFC3630]. When
the Local and Remote TE Router ID sub-TLV is present, it MUST be used
to identify local and remote transport node endpoints for the link
and the Link-ID sub-TLV MUST be ignored. In fact, when the Local and
Remote TE Router ID sub-TLV is specified, the Link-ID sub-TLV MAY be
omitted. The Local and Remote TE Router ID sub-TLV, if specified,
MUST only be specified once. If specified more than once, instances
other than the first will be ignored and the condition SHOULD be
logged for possible action by the network operator.
Malis, et al. Standards Track [Page 10]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20136.2. Reachability Advertisement (Local TE Router ID Sub-TLV)
When an OSPF router is advertising on behalf of multiple transport
nodes, the routing protocol MUST be able to associate the advertised
reachability information with the correct transport node.
For this purpose, a new sub-TLV of the OSPFv2 TE LSA top-level Node
Attribute TLV is introduced. This TLV associates the local prefixes
(see above) to a given transport node identified by the TE Router ID.
The Type field of the Local TE Router ID sub-TLV is assigned the
value 5 (see Section 10). The Length field takes the value 4. The
Value field of this sub-TLV contains the Local TE Router Identifier
encoded over 4 octets.
The format of the Local TE Router ID sub-TLV is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (5) | Length (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV MUST be included as a sub-TLV of the top-level Node
Attribute TLV if the OSPF router is advertising on behalf of one or
more transport nodes having TE Router IDs different from the TE
Router ID advertised in the Router Address TLV. For consistency,
this sub-TLV MUST be included when OSPF is used for the advertisement
of ASON information as described herein. If it is not included in a
Node Attribute TLV, or if a value of 0 is specified for the Local TE
Router Identifier, the Note Attribute TLV will not be used for
determining ASON SCN reachability. Additionally, the condition
SHOULD be logged for possible action by the network operator.
7. Routing Information Dissemination
An ASON routing area (RA) represents a partition of the transport
plane, and its identifier is used within the control plane as the
representation of this partition. An RA may contain smaller RAs
inter-connected by links. ASON RA levels do not map directly to OSPF
areas. Rather, hierarchical levels of RAs are represented by
separate OSPF protocol instances. However, it is useful to align the
RA IDs and area ID in order to facilitate isolation of RAs as
described in Section 11.1.
Malis, et al. Standards Track [Page 11]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
Routing Controllers (RCs) supporting multiple RAs disseminate
information downward and upward in this ASON hierarchy. The vertical
routing information dissemination mechanisms described in this
section do not introduce or imply hierarchical OSPF areas. RCs
supporting RAs at multiple levels are structured as separate OSPF
instances with routing information exchange between levels described
by import and export rules between these instances. The
functionality described herein does not pertain to OSPF areas or OSPF
Area Border Router (ABR) functionality.
7.1. Import/Export Rules
RCs supporting RAs disseminate information upward and downward in the
hierarchy by importing/exporting routing information as TE LSAs. TE
LSAs are area-scoped Opaque LSAs with Opaque type 1 [RFC3630]. The
information that MAY be exchanged between adjacent levels includes
the Router Address, Link, and Node Attribute top-level TLVs.
The imported/exported routing information content MAY be transformed,
e.g., filtered or aggregated, as long as the resulting routing
information is consistent. In particular, when more than one RC is
bound to adjacent levels and both are allowed to import/export
routing information, it is expected that these transformations are
performed in a consistent manner. Definition of these policy-based
mechanisms are outside the scope of this document.
In practice, and in order to avoid scalability and processing
overhead, routing information imported/exported downward/upward in
the hierarchy is expected to include reachability information (see
Section 4) and, upon strict policy control, link topology
information.
7.2. Loop Prevention
When more than one RC is bound to an adjacent level of the ASON
hierarchy and is configured to export routing information upward or
downward, a specific mechanism is required to avoid looping of
routing information. Looping is the re-advertisement of routing
information into an RA that had previously advertised that routing
information upward or downward into an upper or lower level RA in the
ASON hierarchy. For example, without loop-prevention mechanisms,
this could happen when the RC advertising routing information
downward in the hierarchy is not the same one that advertises routing
information upward in the hierarchy.
Malis, et al. Standards Track [Page 12]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20137.2.1. Inter-RA Export Upward/Downward Sub-TLVs
The Inter-RA Export sub-TLVs can be used to prevent the
re-advertisement of OSPF TE routing information into an RA that
previously advertised that information. The type value 13 (see
Section 10) will indicate that the associated routing information has
been exported downward. The type value 12 (see Section 10) will
indicate that the associated routing information has been exported
upward. While it is not required for routing information exported
downward, both sub-TLVs will include the Routing Area (RA) ID from
which the routing information was exported. This RA is not
necessarily the RA originating the routing information but the RA
from which the information was immediately exported.
These additional sub-TLVs MAY be included in TE LSAs that include any
of the following top-level TLVs:
- Router Address top-level TLV
- Link top-level TLV
- Node Attribute top-level TLV
The Type field of the Inter-RA Export Upward and Inter-RA Export
Downward sub-TLVs are respectively assigned the values 12 and 13 (see
Section 10). The Length field in these sub-TLVs takes the value 4.
The Value field in these sub-TLVs contains the associated RA ID. The
RA ID value must be a unique identifier for the RA within the ASON
routing domain.
The format of the Inter-RA Export Upward and Inter-RA Export Downward
sub-TLVs is graphically depicted below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Upward/Downward Type | Length (4) |
| (12/13) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Associated RA ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7.2.2. Inter-RA Export Upward/Downward Sub-TLV Processing
TE LSAs MAY be imported or exported downward or upward in the ASON
routing hierarchy. The direction and advertising RA ID are
advertised in an Inter-RA Export Upward/Downward sub-TLV. They MUST
be retained and advertised in the receiving RA with the associated
routing information.
Malis, et al. Standards Track [Page 13]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
When exporting routing information upward in the ASON routing
hierarchy, any information received from a level above, i.e., tagged
with an Inter-RA Export Downward sub-TLV, MUST NOT be exported
upward. Since an RA at Level N is contained by a single RA at
Level N+1, this is the only checking that is necessary and the
associated RA ID is used solely for informational purposes.
When exporting routing information downward in the ASON routing
hierarchy, any information received from a level below, i.e., tagged
with an Inter-RA Export Upward sub-TLV, MUST NOT be exported downward
if the target RA ID matches the RA ID associated with the routing
information. This additional checking is required for routing
information exported downward since a single RA at Level N+1 may
contain multiple RAs at Level N in the ASON routing hierarchy. In
other words, routing information MUST NOT be exported downward into
the RA from which it was received.
8. OSPFv2 Scalability
The extensions described herein are only applicable to ASON routing
domains, and it is not expected that the attendant reachability (see
Section 4) and link information will ever be combined with global
Internet or Layer 3 Virtual Private Network (VPN) routing. If there
were ever a requirement for a given RC to participate in both
domains, separate OSPFv2 instances would be utilized. However, in a
multi-level ASON hierarchy, the potential volume of information could
be quite large and the recommendations in this section MUST be
followed by RCs implementing this specification.
- Routing information exchange upward/downward in the hierarchy
between adjacent RAs MUST, by default, be limited to reachability
information. In addition, several transformations such as prefix
aggregation are RECOMMENDED to reduce the amount of information
imported/exported by a given RC when such transformations will not
impact consistency.
- Routing information exchange upward/downward in the ASON hierarchy
involving TE attributes MUST be under strict policy control.
Pacing and min/max thresholds for triggered updates are strongly
RECOMMENDED.
- The number of routing levels MUST be maintained under strict policy
control.
Malis, et al. Standards Track [Page 14]

RFC 6827 ASON Routing for OSPFv2 Protocols January 20139. Security Considerations
This document specifies the contents and processing of OSPFv2 TE LSAs
[RFC3630] and [RFC4202]. The TE LSA extensions defined in this
document are not used for Shortest Path First (SPF) computation and
have no direct effect on IP routing. Additionally, ASON routing
domains are delimited by the usual administrative domain boundaries.
Any mechanisms used for securing the exchange of normal OSPF LSAs can
be applied equally to all TE LSAs used in the ASON context.
Authentication of OSPFv2 LSA exchanges (such as OSPF cryptographic
authentication [RFC2328] [RFC5709]) can be used to provide
significant protection against active attacks. [RFC5709] defines a
mechanism for authenticating OSPFv2 packets by making use of the
Hashed Message Authentication Code (HMAC) algorithm in conjunction
with the SHA family of cryptographic hash functions.
RCs implementing export/import of ASON routing information between
RAs MUST also include policy control of both the maximum amount of
information advertised between RAs and the maximum rate at which it
is advertised. This is to isolate the consequences of an RC being
compromised to the RAs to which that subverted RC is attached.
The "Analysis of OSPF Security According to KARP Design Guide"
[OSPF-SEC] provides a comprehensive analysis of OSPFv2 and OSPFv3
security relative to the requirements specified in [RFC6518].
10. IANA Considerations
This document defines new sub-TLVs for inclusion in OSPF TE LSAs.
IANA has assigned values per the assignment policies for the
registries of code points for these sub-TLVs [RFC3630].
The following subsections summarize the required sub-TLVs.
10.1. Sub-TLVs of the Link TLV
This document defines the following sub-TLVs of the Link TLV
advertised in the OSPF TE LSA:
- Local and Remote TE Router ID sub-TLV (10)
- Inter-RA Export Upward sub-TLV (12)
- Inter-RA Export Downward sub-TLV (13)
Codepoints for these sub-TLVs have been allocated in the Standards
Action range of the "Types for sub-TLVs of TE Link TLV (Value 2)"
registry [RFC3630].
Malis, et al. Standards Track [Page 15]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
Note that the same values for the Inter-RA Export Upward sub-TLV and
the Inter-RA Export Downward sub-TLV MUST be used when they appear in
the Link TLV, Node Attribute TLV, and Router Address TLV.
10.2. Sub-TLVs of the Node Attribute TLV
This document defines the following sub-TLVs of the Node Attribute
TLV advertised in the OSPF TE LSA:
- Local TE Router ID sub-TLV (5)
- Inter-RA Export Upward sub-TLV (12)
- Inter-RA Export Downward sub-TLV (13)
Codepoints for these sub-TLVs have been assigned in Standards Action
range of the "Types for sub-TLVs of TE Node Attribute TLV (Value 5)"
[RFC5786].
Note that the same values for the Inter-RA Export Upward sub-TLV and
the Inter-RA Export Downward sub-TLV MUST be used when they appear in
the Link TLV, Node Attribute TLV, and Router Address TLV.
10.3. Sub-TLVs of the Router Address TLV
The Router Address TLV is advertised in the OSPF TE LSA [RFC3630].
Since the TLV had no sub-TLVs defined, a "Types for sub-TLVs of
Router Address TLV (Value 1)" registry has been defined.
The registry guidelines for the assignment of types for sub-TLVs of
the Router Address TLV are as follows:
o Types in the range 0-32767 are to be assigned via Standards
Action.
o Type 0 in the aforementioned Standards Action range (0-32767)
is reserved.
o Types in the range 32768-32777 are for experimental use; these
will not be registered with IANA and MUST NOT be mentioned by
RFCs.
o Types in the range 32778-65535 are not to be assigned at this
time. Before any assignments can be made in this range, there
MUST be a Standards Track RFC that specifies IANA
Considerations that covers the range being assigned.
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This document defines the following sub-TLVs for inclusion in the
Router Address TLV:
- Inter-RA Export Upward sub-TLV (12)
- Inter-RA Export Downward sub-TLV (13)
Codepoints for these sub-TLVs have been allocated in the Standards
Action range of the "Types for sub-TLVs of Router Address TLV
(Value 1)" registry.
Note that the same values for the Inter-RA Export Upward sub-TLV and
the Inter-RA Export Downward sub-TLV MUST be used when they appear in
the Link TLV, Node Attribute TLV, and Router Address TLV.
11. Management Considerations11.1. Routing Area (RA) Isolation
If the RA ID is mapped to the OSPF Area ID as recommended in
Section 2, OSPF [RFC2328] implicitly provides isolation. On any
intra-RA link, packets will only be accepted if the area ID in the
OSPF packet header matches the area ID for the OSPF interface on
which the packet was received. Hence, RCs will only establish
adjacencies and exchange reachability information (see Section 4.0)
with RCs in the same RA. Other mechanisms for RA isolation are
beyond the scope of this document.
11.2. Routing Area (RA) Topology/Configuration Changes
The GMPLS Routing for ASON requirements [RFC4258] dictate that the
routing protocol MUST support reconfiguration and SHOULD support
architectural evolution. OSPF [RFC2328] includes support for the
dynamic introduction or removal of ASON reachability information
through the flooding and purging of OSPF Opaque LSAs [RFC5250].
Also, when an RA is partitioned or an RC fails, stale LSAs SHOULD NOT
be used unless the advertising RC is reachable. The configuration of
OSPF RAs and the policies governing the redistribution of ASON
reachability information between RAs are implementation issues
outside of the OSPF routing protocol and beyond the scope of this
document.
12. Comparison to Requirements in RFC 4258
The following table shows how this document complies with the
requirements in [RFC4258]. The first column contains a requirements
number (1-30) and the relevant section in RFC 4258. The second
column describes the requirement, the third column discusses the
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compliance to that requirement, and the fourth column lists the
relevant section in this document and/or another RFC that already
satisfies the requirement.
Malis, et al. Standards Track [Page 18]

RFC 6827 ASON Routing for OSPFv2 Protocols January 2013Appendix A. ASON Terminology
This document makes use of the following terms:
Administrative domain: (See Recommendation [G.805].) For the
purposes of [G.7715.1], an administrative domain represents the
extent of resources that belong to a single player such as a
network operator, a service provider, or an end-user.
Administrative domains of different players do not overlap amongst
themselves.
Control plane: performs the call control and connection control
functions. Through signaling, the control plane sets up and
releases connections and may restore a connection in case of a
failure.
(Control) Domain: represents a collection of (control) entities that
are grouped for a particular purpose. The control plane is
subdivided into domains matching administrative domains. Within
an administrative domain, further subdivisions of the control
plane are recursively applied. A routing control domain is an
abstract entity that hides the details of the RC distribution.
External NNI (E-NNI): interfaces located between protocol controllers
between control domains.
Internal NNI (I-NNI): interfaces located between protocol controllers
within control domains.
Link: (See Recommendation G.805.) A "topological component" that
describes a fixed relationship between a "subnetwork" or "access
group" and another "subnetwork" or "access group". Links are not
limited to being provided by a single server trail.
Management plane: performs management functions for the transport
plane, the control plane, and the system as a whole. It also
provides coordination between all the planes. The following
management functional areas are performed in the management plane:
performance, fault, configuration, accounting, and security
management.
Management domain: (See Recommendation G.805.) A management domain
defines a collection of managed objects that are grouped to meet
organizational requirements according to geography, technology,
policy, or other structure, and for a number of functional areas
such as Fault, Configuration, Accounting, Performance, and
Security (FCAPS), for the purpose of providing control in a
consistent manner. Management domains can be disjoint, contained,
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RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
or overlapping. As such, the resources within an administrative
domain can be distributed into several possible overlapping
management domains. The same resource can therefore belong to
several management domains simultaneously, but a management domain
shall not cross the border of an administrative domain.
Subnetwork Point (SNP): The SNP is a control-plane abstraction that
represents an actual or potential transport-plane resource. SNPs
(in different subnetwork partitions) may represent the same
transport resource. A one-to-one correspondence should not be
assumed.
Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
for the purposes of routing.
Termination Connection Point (TCP): A TCP represents the output of a
Trail Termination function or the input to a Trail Termination
Sink function.
Transport plane: provides bidirectional or unidirectional transfer of
user information, from one location to another. It can also
provide transfer of some control and network management
information. The transport plane is layered; it is equivalent to
the Transport Network defined in Recommendation G.805.
User Network Interface (UNI): interfaces are located between protocol
controllers between a user and a control domain. Note: There is
no routing function associated with a UNI reference point.
Appendix B. ASON Routing Terminology
This document makes use of the following terms:
Routing Area (RA): an RA represents a partition of the transport
plane, and its identifier is used within the control plane as the
representation of this partition. Per [G.8080], an RA is defined
by a set of subnetworks, the links that interconnect them, and the
interfaces representing the ends of the links exiting that RA. An
RA may contain smaller RAs inter-connected by links. The limit of
subdivision results in an RA that contains two subnetworks
interconnected by a single link.
Routing Database (RDB): a repository for the local topology, network
topology, reachability, and other routing information that is
updated as part of the routing information exchange and may
additionally contain information that is configured. The RDB may
contain routing information for more than one routing area (RA).
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RFC 6827 ASON Routing for OSPFv2 Protocols January 2013
Routing Components: ASON routing architecture functions. These
functions can be classified as protocol independent (Link Resource
Manager (LRM), Routing Controller (RC)) or protocol specific
(Protocol Controller (PC)).
Routing Controller (RC): handles (abstract) information needed for
routing and the routing information exchange with peering RCs by
operating on the RDB. The RC has access to a view of the RDB.
The RC is protocol independent.
Note: Since the RDB may contain routing information pertaining to
multiple RAs (and possibly to multiple layer networks), the RCs
accessing the RDB may share the routing information.
Link Resource Manager (LRM): supplies all the relevant component and
TE link information to the RC. It informs the RC about any state
changes of the link resources it controls.
Protocol Controller (PC): handles protocol-specific message exchanges
according to the reference point over which the information is
exchanged (e.g., E-NNI, I-NNI) and internal exchanges with the RC.
The PC function is protocol dependent.
Appendix C. Changes from RFC 5787
This document contains the following changes from RFC 5787:
1. This document will be on the Standards Track, rather than
Experimental, and reflects experience gained from RFC 5787
implementation and interoperability testing. This also required
changes to the IANA Considerations.
2. There is a new Section 3 on Terminology and Identification to
describe the mapping of key ASON entities to OSPF entities.
3. Sections were reorganized to explain terminology before defining
prefix extensions.
4. There is a new Section 11, Management Considerations, which
describes how existing OSPF mechanisms address ASON requirements
on Routing Area changes.
5. There is a new Section 12, which compares the document to the
requirements in RFC 4258.
6. The prefix format was changed to reference RFC 5786 rather than
defining a separate format and The Node Attribute TLV in RFC 5786
has been updated as a result.
Malis, et al. Standards Track [Page 29]